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// twofish.cpp - modified by Wei Dai from Matthew Skala's twofish.c
// The original code and all modifications are in the public domain.
#include "pch.h"
#include "twofish.h"
#include "misc.h"
NAMESPACE_BEGIN(CryptoPP)
// compute (c * x^4) mod (x^4 + (a + 1/a) * x^3 + a * x^2 + (a + 1/a) * x + 1)
// over GF(256)
static inline unsigned int Mod(unsigned int c)
{
static const unsigned int modulus = 0x14d;
unsigned int c2 = (c<<1) ^ ((c & 0x80) ? modulus : 0);
unsigned int c1 = c2 ^ (c>>1) ^ ((c & 1) ? (modulus>>1) : 0);
return c | (c1 << 8) | (c2 << 16) | (c1 << 24);
}
// compute RS(12,8) code with the above polynomial as generator
// this is equivalent to multiplying by the RS matrix
static word32 ReedSolomon(word32 high, word32 low)
{
for (unsigned int i=0; i<8; i++)
{
high = Mod(high>>24) ^ (high<<8) ^ (low>>24);
low <<= 8;
}
return high;
}
inline word32 Twofish::Base::h0(word32 x, const word32 *key, unsigned int kLen)
{
x = x | (x<<8) | (x<<16) | (x<<24);
switch(kLen)
{
#define Q(a, b, c, d, t) q[a][GETBYTE(t,0)] ^ (q[b][GETBYTE(t,1)] << 8) ^ (q[c][GETBYTE(t,2)] << 16) ^ (q[d][GETBYTE(t,3)] << 24)
case 4: x = Q(1, 0, 0, 1, x) ^ key[6];
case 3: x = Q(1, 1, 0, 0, x) ^ key[4];
case 2: x = Q(0, 1, 0, 1, x) ^ key[2];
x = Q(0, 0, 1, 1, x) ^ key[0];
}
return x;
}
inline word32 Twofish::Base::h(word32 x, const word32 *key, unsigned int kLen)
{
x = h0(x, key, kLen);
return mds[0][GETBYTE(x,0)] ^ mds[1][GETBYTE(x,1)] ^ mds[2][GETBYTE(x,2)] ^ mds[3][GETBYTE(x,3)];
}
void Twofish::Base::UncheckedSetKey(const byte *userKey, unsigned int keylength, const NameValuePairs &)
{
AssertValidKeyLength(keylength);
unsigned int len = (keylength <= 16 ? 2 : (keylength <= 24 ? 3 : 4));
SecBlock<word32> key(len*2);
GetUserKey(LITTLE_ENDIAN_ORDER, key.begin(), len*2, userKey, keylength);
unsigned int i;
for (i=0; i<40; i+=2)
{
word32 a = h(i, key, len);
word32 b = rotlFixed(h(i+1, key+1, len), 8);
m_k[i] = a+b;
m_k[i+1] = rotlFixed(a+2*b, 9);
}
SecBlock<word32> svec(2*len);
for (i=0; i<len; i++)
svec[2*(len-i-1)] = ReedSolomon(key[2*i+1], key[2*i]);
for (i=0; i<256; i++)
{
word32 t = h0(i, svec, len);
m_s[0][i] = mds[0][GETBYTE(t, 0)];
m_s[1][i] = mds[1][GETBYTE(t, 1)];
m_s[2][i] = mds[2][GETBYTE(t, 2)];
m_s[3][i] = mds[3][GETBYTE(t, 3)];
}
}
#define G1(x) (m_s[0][GETBYTE(x,0)] ^ m_s[1][GETBYTE(x,1)] ^ m_s[2][GETBYTE(x,2)] ^ m_s[3][GETBYTE(x,3)])
#define G2(x) (m_s[0][GETBYTE(x,3)] ^ m_s[1][GETBYTE(x,0)] ^ m_s[2][GETBYTE(x,1)] ^ m_s[3][GETBYTE(x,2)])
#define ENCROUND(n, a, b, c, d) \
x = G1 (a); y = G2 (b); \
x += y; y += x + k[2 * (n) + 1]; \
(c) ^= x + k[2 * (n)]; \
(c) = rotrFixed(c, 1); \
(d) = rotlFixed(d, 1) ^ y
#define ENCCYCLE(n) \
ENCROUND (2 * (n), a, b, c, d); \
ENCROUND (2 * (n) + 1, c, d, a, b)
#define DECROUND(n, a, b, c, d) \
x = G1 (a); y = G2 (b); \
x += y; y += x; \
(d) ^= y + k[2 * (n) + 1]; \
(d) = rotrFixed(d, 1); \
(c) = rotlFixed(c, 1); \
(c) ^= (x + k[2 * (n)])
#define DECCYCLE(n) \
DECROUND (2 * (n) + 1, c, d, a, b); \
DECROUND (2 * (n), a, b, c, d)
typedef BlockGetAndPut<word32, LittleEndian> Block;
void Twofish::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
word32 x, y, a, b, c, d;
Block::Get(inBlock)(a)(b)(c)(d);
a ^= m_k[0];
b ^= m_k[1];
c ^= m_k[2];
d ^= m_k[3];
const word32 *k = m_k+8;
ENCCYCLE (0);
ENCCYCLE (1);
ENCCYCLE (2);
ENCCYCLE (3);
ENCCYCLE (4);
ENCCYCLE (5);
ENCCYCLE (6);
ENCCYCLE (7);
c ^= m_k[4];
d ^= m_k[5];
a ^= m_k[6];
b ^= m_k[7];
Block::Put(xorBlock, outBlock)(c)(d)(a)(b);
}
void Twofish::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
word32 x, y, a, b, c, d;
Block::Get(inBlock)(c)(d)(a)(b);
c ^= m_k[4];
d ^= m_k[5];
a ^= m_k[6];
b ^= m_k[7];
const word32 *k = m_k+8;
DECCYCLE (7);
DECCYCLE (6);
DECCYCLE (5);
DECCYCLE (4);
DECCYCLE (3);
DECCYCLE (2);
DECCYCLE (1);
DECCYCLE (0);
a ^= m_k[0];
b ^= m_k[1];
c ^= m_k[2];
d ^= m_k[3];
Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
}
NAMESPACE_END
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